Re: [PATCH] rwsem: reduce spinlock contention in wakeup code path

[Ingo Molnar]

* Waiman Long <waiman.long@xxxxxx> wrote:

> > I think Waiman's patches (even the later ones) made the queued rwlocks 
> > be a side-by-side implementation with the old rwlocks, and I think 
> > that was just being unnecessarily careful. It might be useful for 
> > testing to have a config option to switch between the two, but we 
> > might as well go all the way.
> 
> It is not actually a side-by-side implementation. A user can choose 
> either regular rwlock or the queue one, but never both by setting a 
> configuration parameter. However, I now think that maybe we should do it 
> the lockref way by pre-determining it on a per-architecture level 
> without user visible configuration option.

Well, as I pointed it out to you during review, such a Kconfig driven 
locking API choice is a no-go!

What I suggested instead: there's absolutely no problem with providing a 
better rwlock_t implementation, backed with numbers and all that.

Thanks,

	Ingo
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